PHENOMENA ACCOMPANYING FERTILIZATION 327 



witsch (1915), by Davis (1916) and by Naville (1931), there is little 

 evidence of reduction in number either before or after nuclear 

 fusion, with the exception of Naville's account, and this is difficult 

 to harmonize with meiotic phenomena in either protozoa or metazoa. 

 Erdmann (1917) has shown that so-called reduction nuclei inside 

 the spore are masses of chromatin or perhaps glycogen, which serve 

 a purpose in the formation of the spore membrane. The extremely 

 minute size of the nuclei and the technical difficulties make the 

 general problem very difficult to solve in Cnidosporidia. 



From the foregoing review it is apparent that the changes of a 

 cumulative character are taking place during the vegetative activi- 

 ties in all types of organization. Such changes are manifested by 

 structural or functional peculiarities at different stages, the most 

 marked of which are at periods of maturity and old age. Some of 

 these are peculiar to certain types only, e. g., the old age structural 

 differentiations of Mycetozoa and Sporozoa. Others, particularly 

 those occurring at maturity, are more universal but differ in degree 

 in different cases, the least evident being those of hologametes and 

 conjugating Infusoria, and the most evident are those in which 

 complete anisogamy occurs. One widely spread effect of such dif- 

 ferentiation is the phenomenon of meiosis or reduction in the number 

 of chromosomes. This also occurs at various periods, furnishing 

 a basis for the categories of conjugant meiosis, gametic meiosis and 

 zygotic meiosis. 



Whatever may be the interpretation of the phenomenon, the fact 

 is obvious that all products of fertilization are labile, active organ- 

 isms quite different in character from the conjugants, hologametes, 

 or gametes which participated in their production. Apparently 

 the same protoplasm, however, is continuous from the old to the 

 young, and during transition certain processes, here described as 

 disorganization and reorganization, have taken place. These proc- 

 esses, as I believe, are responsible for the renewal of vitality and 

 for the inaguration of a new life cycle in a new organism, evidence 

 for which is given in the following chapter. 



